The present disclosure relates generally to substrate ion exchange systems and methods of maintaining and controlling such systems. More particularly, the various embodiments in this disclosure relate to ion exchange systems for glass, glass-ceramic and ceramic articles with single- and multi-component molten ion exchange baths, along with methods for maintaining and controlling such systems.
Ion exchange (IOX) processes are employed to vary and control the concentration of metal ions in various glass, glass-ceramic and ceramic substrates through localized compositional modifications. These compositional modifications in the substrates can be used to modify certain substrate properties. For example, alkali metal ions (e.g., Na and K ions) may be imparted into surface regions of substrates as a strengthening mechanism. As another example, various heavy metal ions (e.g., Ag, Cu and Zn ions) can be imparted into surface regions of substrates to provide the substrate with anti-microbial properties. In some instances, the substrate may include some alkali metal ions enhancing the strength of the substrate (hereinafter, such substrates may be referred to as “strengthened substrates”), and may be further modified with one or more heavy metal ions to provide anti-microbial properties.
These IOX processes often involve the immersion of substrates in a molten salt bath at elevated temperatures. The molten salt bath includes metal ions intended to be introduced into the substrates. Ions in the substrates are exchanged with the metal ions in the bath during the IOX processes. As such, the control of the concentration of the metal ions in the bath is important in controlling the quantity of ions that are exchanged with the substrates during the IOX processes. These concentration levels can change over time as metal ions in the bath are consumed and replaced by ions exchanged from the substrate (e.g., “effluent ions”). At some point in time, the concentration of the metal ions in the bath falls below a practical level for imparting the desired property in the substrate through the IOX process. In manufacturing, however, it is often not practical or cost effective to use a “fresh” ion exchange bath for each substrate ion exchange run to account for these metal ion consumption issues.
Accordingly, there is a need to develop systems and methods suitable for manufacturing operations that take into account the changes in metal ion concentration in ion exchange baths over time associated with IOX processing of substrates.